1. Field of the Invention
This invention relates to a communication system having a plurality of communication procedure control functions.
Further, the invention relates to a communication system comprising a telephone control unit which accommodates at least one central office network line and a plurality of extensions, and which is adapted to control line connection between the central office network line and the plurality of extensions, telephones connected to the extensions, and at least one data processor connected to the extensions.
2. Description of the Prior Art
By virtue of a reduction in cost and an improvement in the capability of modern information processors, it has now become possible to install these information processors (e.g., personal computers) in ordinary offices. Moreover, these devices can be connected to other computers via central office network lines to make possible the retrieval and exchange of information.
In the prior art, however, these information processors are connected to pay station lines dedicated to special equipment separate from the other telephone equipment located in the office. Moreover, in most cases these processors are equipped with private telephones and calls are both sent and received via dedicated lines therefor. Even when a call is received a response is made separately by the telephones dedicated to the aforementioned equipment provided on the information processors or installed in the vicinity thereof, and when necessary a line is switched over from a telephone to the information processor side by a manual operation. Alternatively, a received call is answered in the form of an overall data transmission without providing for a telephone.
Consequently, when the information processors are not being used these idle lines cannot be employed by the other telephones. This represents a significant waste.
In an effort to solve this problem, it has become possible to connect a signal information processor to the extensions of a telephone control unit which performs network control between the telephones and lines, and transfer the call of a response by another telephone under well-known telephone transfer control.
In the transfer processing, however, it is necessary first to search for the extension telephone number already assigned to the information processor, then input the pertinent extension telephone number and execute actual transfer processing. With this arrangement, extremely complicated processing cannot be avoided and the response timer of the information processor on the calling side can run out of time and result in the call being disconnected, thereby running up an unnecessary telephone fee.
There is known in the art a communication device having two communication control functions, namely a communication procedure control function in accordance with the "Personal Computer Communication Device Recommendation System" (hereinafter referred to as the "JUST-PC communication system") of Notification No. 971 of the Ministry of Posts and Telecommunications, and a facsimile communication procedure control function.
In a communication device having such a JUST-PC communication procedure control function and a facsimile communication procedure control function, a problem which arises is that after a call is automatically received, it cannot be determined whether the call received from the other party's terminal is a call for the purpose of communication in accordance with the JUST-PC communication system or a call for the purpose of communication in accordance with the facsimile communication system.